1. Field of the Invention
The present invention is related to a driving method and apparatus for driving an LCD panel, and more particularly, to a driving method and apparatus for reducing a vertical-line effect by randomly changing a gate-on sequence, so as to enhance image quality.
2. Description of the Prior Art
A liquid crystal display (LCD) monitor has characteristics of light shape, low power consumption, zero radiation, etc., and has been widely used in many information technology (IT) products, such as computer systems, mobile phones, and personal digital assistants (PDAs). The operating principle of the LCD is based on the fact that liquid crystals in different twist status can result in different polarization and refraction effects on lights. Thus, the liquid crystals can control penetration amount of light by arranging in different twist status, so as to produce various brightness of light output and diverse gray levels of red, green and blue lights.
Please refer to FIG. 1. FIG. 1 is a schematic diagram of a thin-film-transistor (TFT) LCD monitor 10 according to the prior art. The LCD monitor 10 includes an LCD panel 100, a control circuit 102, a data-line-signal output circuit 104, a scan-line-signal output circuit 106, and a voltage generator 108. The LCD panel 100 is formed with two substrates, and LCD layers are stuffed between the substrates. One substrate includes a plurality of data lines 110, a plurality of scan lines (or gate lines) 112 perpendicular to the data lines 110, and a plurality of TFTs 114. The other substrate includes a common electrode for providing a common voltage Vcom generated by the voltage generator 108. For the sake of brevity, FIG. 1 reveals only four TFTs 114, but in a real case, there is one TFT 114 set at each intersection of a data line 110 and a scan line 112 on the LCD panel 100. In other words, the plurality of TFTs 114, each corresponding to a pixel, form a matrix on the LCD panel 100, and the data lines 110 and the scan lines 112 are corresponding to columns and rows of the matrix. In addition, a circuit effect resulted from the two substrates of the LCD panel 100 can be regarded as equivalent capacitors 116.
A driving process of the prior art TFT LCD monitor 10 is described in details as follows. When the control circuit 102 receives a horizontal synchronization signal 118 and a vertical synchronization signal 120, the control circuit 102 generates corresponding control signals for the data-line-signal output circuit 104 and the scan-line-signal output circuit 106. The data-line-signal output circuit 104 and the scan-line-signal output circuit 106 generate input signals for the data lines 110 and the scan lines 112 according to the control signals, in order to control the TFTs 114 and voltage differences of the equivalent capacitors 116. The voltage differences change twist of liquid crystals and corresponding penetration amount of light so as to display the display data 122 on a panel.
On the other hand, as those skilled in the art recognized, every color is composed of red, green, and blue, named three primary colors. Therefore, in the LCD panel 100, each dot is practically composed of pixels corresponding to red, green, and blue. Please refer to FIG. 2. FIG. 2 illustrates a schematic diagram of pixel alignment in the LCD panel 100. In the FIG. 2, R, G, B respectively represent pixels corresponding to red, green, and blue, G1˜Gn represent gate driving signals outputted by the scan line signal output circuit 106, and S1˜S2m represent source driving signals outputted by the data line signal output circuit 104. When displaying images, the scan line signal output circuit 106 outputs the gate-driving signals G1˜Gn for sequentially turning on pixels in each row, and the data line signal output circuit 104 controls R, G, B pixels of each dot for generating corresponding colors and gray levels according to the display data 122.
In order to save the number of data line signals and distribute pixels more effectively, the prior art provides an LCD, which controls pixels in the same row by at least two gate-driving signals. Please refer to FIG. 3. FIG. 3 illustrates a schematic diagram of pixel alignment in a prior art LCD panel 300. As shown in FIG. 3, pixels in a row are controlled by two gate-driving signals (e.g. the first row is controlled by G1 and G2, and the second row is controlled by G3 and G4, etc). When displaying images through the LCD panel 300, a scan line signal output circuit of the LCD panel 300 outputs gate-driving signals G1˜G2n for turning on pixels in each row, so as to display images according to source driving signals S1˜Sm. In this case, odd and even pixels in a row are alternatively turned on, and pixels in adjacent rows are controlled by a source driving signal, so that the LCD panel 300 has a vertical-line effect, which lowers image quality and reduce the application range.